CVE-2026-91187

Improper Verification of Cryptographic Signature vulnerability in dashbit nimble_zta allows an unauthenticated remote attacker to authenticate as an arbitrary Cloudflare service token. Applications using the Cloudflare Zero Trust authentication strategy are affected. verify_token/2 in lib/nimble_zta/cloudflare.ex matches the result of JOSE.JWT.verify/2 against {_, token, _s}, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the cf-access-jwt-assertion header, carrying the expected iss claim and the seven service token claims. verify_iss/2 reads the iss claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity. This issue affects nimble_zta: from 0.1.2 before 0.1.3.

CVSS

No CVSS.

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-91187.html
https://github.com/dashbitco/nimble_zta/commit/6458fd18a5ba41166d4973214c519e98fe05b72d
https://github.com/dashbitco/nimble_zta/commit/bc004b70985ae5763901baab3a4e204047899768
https://github.com/dashbitco/nimble_zta/security/advisories/GHSA-rj24-g8cc-g7g2
https://osv.dev/vulnerability/EEF-CVE-2026-91187

Configurations

No configuration.

History

24 Sep 2026, 14:18

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-24 14:18

Updated : 2026-09-24 19:39

NVD link : CVE-2026-91187

Mitre link : CVE-2026-91187

CVE.ORG link : CVE-2026-91187

JSON object : View

Products Affected

No product.

CWE

CWE-347

Improper Verification of Cryptographic Signature

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Applications using the Cloudflare Zero Trust authentication strategy are affected.\n\nverify_token/2 in lib/nimble_zta/cloudflare.ex matches the result of JOSE.JWT.verify/2 against {_, token, _s}, which discards the boolean verification result and returns the decoded token after a failed signature check. The attacker sends a forged JWT in the cf-access-jwt-assertion header, carrying the expected iss claim and the seven service token claims. verify_iss/2 reads the iss claim from the forged token, so it rejects nothing, and the service token path then returns those claims as the authenticated identity.\n\nThis issue affects nimble_zta: from 0.1.2 before 0.1.3."}], "lastModified": "2026-09-24T19:39:45.600", "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}